The Interstellar Standard Warship Classification System (ISWCS) is a warship typology agreed upon by the League of Interstellar Civilisations for ease of regulation and management.
It should be noted that not all signatory navies use the standardised terminology. Most famously, the Reunification Navy uses the terms ‘Light Cruiser’ and ‘Heavy Cruiser’ instead of the ISWCS-defined ‘Missile Cruiser’ and ‘Gun Cruiser’.
Overarching Definitions
The ISWCS uses three main definitions to help in its classification system, differentiating between ‘dedicated warships’, ‘multi-role warships’, and ‘carriers’.
Dedicated warships are vessels designed solely for high-intensity combat missions, with their primary function to engage and destroy other starships. Orbital bombardment may also be a secondary function, and larger types may also be able to fulfil transport or carrying missions, but these are secondary to the primary function and intended solely to improve the vessel’s ability to conduct high-end warfighting operations.
Multi-role warships are vessels designed to able to perform both low- and high-end mission sets. This means they must be capable of performing long patrol, exploration, humanitarian, policing, and power-projection missions in addition to high-intensity warfighting. This means they are typically less capable combat ships, for their size, but are more flexible and far more useful in peacetime. Most multi-role ships will also be able to conduct (limited) transport and carrying operations.
Carriers are vessels designed primarily around hangar and transport capacity. Their primary mission-sets are humanitarian aid, patrol, and atmospheric assault, though they will also often provide pickets during fleet operations. Only carriers and large lineships are generally capable of carrying full-size Interceptors.
N.B. - with this is mind, transports, landing ships, and assault ships are effectively types of carrier that are not capable of carrying full-size interceptors. This represents a significant expense and requires them to be notably larger, and hence is often omitted in ships intended to specialise in atmospheric landings.
Lineships are vessels designed to be able to fight in the main line of battle, and therefore take enormous punishment from their opposite numbers.
Other kinds of ships are considered - the definitions provided here are for terms that refer to multiple classifications
A primary accelerator battery is considered a ‘significant number of starship-class mass drivers, intended for the primary function of engaging and destroying other warships’.
Classifications
Patrol Ship - A small, short-ranged warship designed for local policing work. Occasionally might even be a spaceship, lacking Otherlight travel capabilities.
Cutter - The smallest type of multi-role warship, designed primarily for police work rather than warfighting.
Corvette - A relatively short-ranged type of multi-role warship, designed primarily for work in its own system. Generally the purview of smaller powers, with most larger civilisations preferring frigates instead.
Destroyer - The smallest type of dedicated warship. Usually low-endurance but heavily-armed for its size, with both missile arrays and a primary accelerator battery.
Frigate - A small multi-role warship, often slightly larger than destroyers. Usually lack a primary accelerator battery but have high-endurance and relatively roomy hangar bays.
Missile Cruiser/Light Cruiser - A larger multi-role warship designed to fulfil almost any possible duty a navy warship might face. Lacks a primary accelerator battery.
Gun Cruiser/Heavy Cruiser - A large multi-role warship designed to fulfil almost any possible duty a navy warship might face. Typically slightly larger than light cruisers due to being armed with a primary accelerator battery.
3rd-Rate Lineship - An enormous multi-role warship designed to be capable of fighting in the main line of battle. Carries a capital-class primary accelerator battery alongside heavy secondary armaments and enormous hangar spaces. Able to deploy significant atmospheric forces.
2nd-Rate Lineship - The largest type of dedicated warship, designed to be capable of fighting in the line of battle. Carries a capital-class primary accelerator battery alongside heavy secondary armament. Typically features smaller hangar facilities than 3rd-rates.
1st-Rate Lineship - The largest type of multi-role warship, designed to be capable of fighting in the line of battle. Carries a capital-class primary accelerator battery and can deploy very large atmospheric forces. 1st-rates are very rare and the largest kind of military starship.
Escort Carrier - The smallest type of carrier, designed primarily for patrol and escort work.
Fleet Carrier - The largest type of carrier, designed to provide fleet pickets and atmospheric assault capacity.
Assault Carrier - A large carrier capable of landing in atmosphere for direct planetary assaults, but also capable of performing regular carrier duties. Generally much larger than a standard assault ship.
Landing Ship - A starship designed to land equipment on planetary surfaces.
Assault Ship - A starship designed to conduct contested landing operations on planetary surfaces.
Fleet Transport - A starship designed to carry equipment and landing craft for planetary landings or assaults, but which is not itself atmospheric-capable.
Monitor - A starship designed with the primary mission of conducting orbital bombardments on hostile worlds. Typically lacks the defensive and sensor capability for starside operations; sometimes atmosphere capable.
Additional Classifications
There are a number of classifications that are widely used and accepted but which are technically not included in the the ISWCS system. Virtually all of these originate with the Reunification Navy, though several have been adopted by others.
Escort Destroyer - A variant of destroyer built for high-endurance in order to better perform convoy escort, hunter-killer, and patrol missions. Still lack the multi-role functionality of cutters and frigates regarding planetary operations and civilian policing, mainly intended for defending against commerce raiding.
Heavy Frigate - A type of frigate that carries a primary accelerator battery. Technically interchangeable with regular frigates under the ISWCS system.
Supercruiser - A type of cruiser armed with a Class IV primary accelerator battery. Initially adopted for an RN programme, but several other navies developed similar ships. Many other navies prefer the term ‘Large Cruiser’, but this was not used in the RN due to the potential confusion with the term ‘Heavy Cruiser’.
Battlecruiser - A type of lineship designed to be the smallest-possible ship still capable of operating in the line of battle. This makes them faster and more manoeuvrable than other ratings, though typically involves giving up any multi-role capabilities.
Light Carrier - A type of carrier designed to fulfil the fleet carrier role in a much smaller package. Generally entails coupling the engines and point-defences of a fleet carrier with the size of an escort carrier (usually slightly larger). Small air/spacegroup but very capable hull.
Fleet Auxiliary - A kind of multi-purpose fleet support ship, equipped with a Factory Module but also armed to a reasonable standard. To some extent they resemble cruisers that sacrifice a significant portion of their other capabilities in return to be able to conduct fleet support/replenishment operations.